Existing Water Pump pliers have the common characteristic of jaws offset at an angle to the Plier handles and a pivot post, in the form of a bolt or rivet, mounted in the area rearward of the jaw on one of the handles and projecting through an elongated slot on the other handle. In such pliers, means for enabling selective spacing of the distance between the jaws is variously provided by spaced apart ridges or teeth along the inside long edge of the slot adapted for incremental selective binding engagement with the pivot post. Another well known method of providing distance adjustment between the jaws in such pliers is the provision of spaced apart arcuate ridges on the interfacing surfaces adjacent the pivot point. All such tools in order to be adjusted to the size of a particular workpiece to be gripped between the jaws, require a two handed operation when the handles are pulled apart to permit a sliding action of the pivot post along the slot to move the jaws to approximately the desired workpiece size.
Further types of pliers are adapted to slideably close upon a workpiece in response to manual closing of the handles and, in response to contact with the workpiece, automatically lock against further sliding action by engaging suitable teeth and thereby shift from a sliding to a pivoting mode whereby continued exertion of manual force on the handles increases the gripping action upon the workpiece.
This gripping action upon the workpiece is a function of the relationship between the length of the operating handles and the length of the jaws pivoting around the pivot post (typically in a ratio of around 5:1). Therefore a considerable portion of the torque applied to the operating handle or handles is required to grip the workpiece to be operated meaning the workpiece can seldom be operated by such a device if it is itself tight to operate. In certain circumstances it would be a considerable advantage if the pliers could be locked upon the workpiece. The existing designs are unable to include this function.
The pivot post locking action, whether by spaced apart ridges, teeth or arcuate ridges on the infacing surfaces, means that the jaws/handles are seldom in the optimum position prior to the shift from sliding to a pivoting mode which results in a variable gripping action upon the workpiece.